This application claims the benefit of and priority to Canadian Application 2274402 filed on Jun. 11, 1999.
The present invention relates to a damper for an overhead cable such as cables of electrical transmission lines.
Wind blowing across a suspended conductor of a transmission line is a very well known source of damage. It induces vibrations which, under resonant conditions, build up to large amplitudes resulting in destructive forces on the conductor. To alleviate this problem, there is known to install a damping device on the conductor, which absorbs the vibration energy. For example, torsional dampers are devices comprising two ball-shaped weights rigidly connected together and fixed on the side of the conductor. When a vertical vibration is induced in the conductor, it is transferred to the weight which rotates in a plan perpendicular to the conductor, inducing therein a torsional movement which is attenuated much more quickly than the vibrational movement. In dampers of the type known as Stockbridge, two weights are suspended on each side of a length of cable called xe2x80x9cmessengerxe2x80x9d. When the conductor vibrates, it excites the weights generating a flexion in the messenger. The strands in the messenger rub against each other, dissipating the energy. The above described dampers are efficient in reducing wind vibrations, but lack endurance and need to be replaced often, especially in harsh climates.
Also known in the art is U.S. Pat. No. 4,167,646 (MATHIEU). Mathieu discloses a vibration damper for overhead conductors, having two weight each connected to a rigid arm, each arm being themselves connected through an elastomer ball to a clamp attached to the conductor. The use of an elastomer joint allows a more solid connection compared to the traditional messenger. However, ball-shaped elastomer joints are relatively difficult and therefore expensive to manufacture and install.
Other related art includes U.S. Pat. No. 2,094,899 (D. MacINTYRE); U.S. Pat. No. 2,688,047 (D. MacINTYRE); U.S. Pat. No. 3,314,503 (V.H. NEUBERT); U.S. Pat. No. 3,662,08 (SMREKAR); U.S. Pat. No. 3,692,919 (ROSTOKER); U.S. Pat. No. 3,711,624 (DULHUNTY); U.S. Pat. No. 3,773,967 (STURM): U.S. Pat. No. 3,780,207 (CROSBY et al.); U.S. Pat. No. 3,904,811 (OTSUKI et al.); U.S. Pat. No. 4,011,397 (BOUCHE); U.S. Pat. No. 4,113,979 (TORR et al.); U.S. Pat. No. 4,140,868 (TUTTLE); U.S. Pat. No. 4,159,393 (DULHUNTY); U.S. Pat. No. 4,167,646 (MATHIEU); U.S. Pat. No. 4,223,176 (HAWKINS); U.S. Pat. No. 4,259,541 (BOUCHE); U.S. Pat. No. 4,278,833 (HAWKINS); U.S. Pat. No. 4,523,053 (RAWLINS); U.S. Pat. No. 4,525,596 (DIANA); U.S. Pat. No. 4,527,009 (HAWKINS); U.S. Pat. No. 4,533,785 (RIGANTI); U.S. Pat. No. 4,554,402 (HAWKINS); U.S. Pat. No. 4,554,403 (HEARNSHAW); U.S. Pat. No. 4,620,059 (SHERMAN); U.S. Pat. No. 4,620,060 (PERINETTI); U.S. Pat. No. 4,680,424 (HAWKINS); U.S. Pat. No. 4,714,799 (HAWKINS); U.S. Pat. No. 4,777,327 (RICHARDSON, Jr.); U.S. Pat. No. 4,808,766 (BUCKNER et al.); and U.S. Pat. No. 5,801,329 (SCHMIDT). None of these patents disclose a resistant damper for overhead conductors which is relatively easy and inexpensive to manufacture.
It is therefore an object of the present invention to provide a damper for an overhead cable that is resistant, even in harsh climates.
It is another object of the invention to provide such a damper that is relatively easy and in expensive to manufacture .
Accordingly, the present invention provide a damper for an overhead cable, comprising:
a support member having a first end provided with a connecting means for connecting said support member to the overhead cable, and a second end having a support axis extending substantially horizontally when the damper hangs from the overhead cable, the support member further including an axial member mounted along the support axis and rigidly connected to the second end, the axial member being provided with at least one pair of stops;
a first dampening member having an arm and a weight connected thereto, the arm having an end pivotally connectable to the support axis, the end of the arm being provided with at least one pair of stops corresponding to and cooperating with the at least one pair of stops of the axial member for limiting a pivotal movement of the first dampening member in both directions;
resilient means located between the pairs of stops of the axial member and the corresponding pairs of stops of the arm for limiting in a resilient manner the pivotal movement of the first dampening member around the support axis; and
restraining means for restraining a movement of the end of the arm of the first dampening member along the support axis.
Other features and advantages of the present invention will be better understood upon reading the following non-restrictive description of embodiments thereof with reference to the appended drawings.